1. Field of the Invention
This invention pertains generally to inhalation therapy devices, and more particularly to a inhalation therapy device which may be used in conjunction with a nebulizer to store medicinal aerosol during patient exhalation, to be delivered the subsequent patient inhalation.
2. Description of the Background Art
Inhalation delivery systems of various types have been widely used for inhalation delivery of aerosols containing medication or other constituents to the conductive airways of the lung and the gas exchange regions of the deep lung. Aerosols are relatively stable suspension of finely divided droplets or solid particles in a gaseous medium, usually in air. When inhaled, aerosol particles may be deposited by contact upon the various surfaces of the respiratory tract leading to potential injury, desirable therapeutic action, or planned diagnostic behavior depending on the particular properties of the particles. Inhalable aerosols are those consisting of particles between 1 and 5 micrometers in aerodynamic equivalent diameter.
Because of the high permeability of the lung and the copious blood flow, medications depositing in the lung can readily enter the blood for action throughout the body, while other medications can directly influence the airway epithelium and effect responses via various airway receptors. Properly generated and formulated aerosols can therefore be helpful in medical treatment. As tracers of airflow or indicators of lung responses, other types of aerosol particles deposited in the lung can also be a valuable diagnostic tool.
A nebulizer produces aerosol of fine particles by breaking a fluid into fine droplets and dispersing them into a flowing stream of gas. The droplet size from a medical nebulizer is considerably smaller than a conventional spray atomizer. Medical nebulizers are designed to convert water or aqueous solutions or colloidal suspensions to aerosols of fine, inhalable droplets that can enter the lungs of a patient during inhalation and deposit on the surface of the respiratory airways.
Pneumatic (compressed gas) medical nebulizers heretofore developed typically provide approximately 15 to 30 microliters of aerosol per liter of gas in finely divided droplets with volume or mass median diameters in the respirable range of 2 to 4 micrometers. Nebulizer gas flow rates typically vary between 6 and 8 L/min.
The inhalation therapy device most often used in conjunction with the nebulizer typically consists of a tee, mouthpiece, and storage tube. The tee consists of 3 branches with corresponding ports for connection of the nebulizer, mouthpiece, and storage tubing. The mouthpiece provides the means for connection to the patient. The storage tube is typically 60 ml in volume and is intended to store some of the aerosol produced by the nebulizer during exhalation. The nebulizer is connected to a compressed gas source and aerosol is caused to flow into the tee and, during inhalation, to the patient. During exhalation the volume and flow of the exhaled gas from the patient is far greater than the flow coming from the nebulizer, resulting in almost the majority of aerosolized medication delivered by the nebulizer entering the ambient environment, where it is lost to the patient. More effective means of storing aerosol can not be realized by increasing the volume of the storage tube because it causes the patient to rebreathe an unacceptable amount of exhaled gas.
A widely used device, the Circulaire, works in conjunction with a nebulizer as previously described and attempts to circumvent the problem of rebreathed gas by storing aerosol in a collapsible aerosol storage bag and is similar to the device described and illustrated in U.S. Pat. No. 5,020,530. The Circulaire prevents exhaled gas from entering the aerosol storage bag through means of a check valve which allows only gas and aerosol to exit the aerosol storage bag. This approach is not very successful because much of the medication stored in the aerosol storage bag is lost as the result of impaction of aerosol particles on the check valve resulting in less medication delivered to the patient than with the previously mentioned tee. The check valve within the Circulaire also has the additional disadvantage of changing the mass median aerodynamic diameter of the aerosol to less than 1 micron, which is below the practical respirable range for aerosol deposition within the human lung.
Therefore, a need exists for a inhalation therapy device which can work in conjunction with a nebulizer to store aerosol produced by the nebulizer during the patients exhalation to be delivered to the patient on the subsequent inhalation. The present invention satisfies that need and has the further advantage of not adversely affecting the mass median aerodynamic diameter of the aerosol delivered to the patient.
The present invention generally pertains to a inhalation therapy device designed to function with existing nebulizers and provides the means for a more effective and inexpensive aerosol therapy than prior art.
By way of example and not of limitation, the present invention employs a collapsible aerosol storage bag. The aerosol storage bag has one opening which connects to the end of a dual port member. One port is in fluid communication with the connecting port for the nebulizer. The geometry of the port in fluid communication with the connecting port for the nebulizer is such that the flow of gas exiting the dual port member and entering the aerosol storage bag is a coherent laminar jet. A coherent laminar jet has the two primary properties of retaining roughly the same cross sectional area of the port of exit and not mixing with the other gas already in the aerosol storage bag. During patient exhalation the aerosol storage bag becomes partially inflated with exhaled gas during the first part of exhalation. The laminar coherent aerosol jet exits the dual port member and remains coherent until reaching the end of the aerosol storage bag, at which time it diverges and expels all exhaled gas from the aerosol storage bag, thus filling the aerosol storage bag with aerosol. All escaping gas exits the aerosol storage bag via the remaining port of the dual port member, where it escapes into the ambient environment through the ambient port. The remaining dual port of the dual port member, in addition to providing means for escaping gas from the aerosol storage bag, is also in fluid communication with the ambient port and the mouthpiece. Upon inhalation, the patient inhales the aerosol within the aerosol storage bag, the aerosol produced by the nebulizer during inhalation, and ambient air through the ambient port. The cycle is than repeated indefinitely.
An object of the invention is to provide a inhalation therapy device which can store aerosol produced during exhalation for delivery to the patient on the subsequent inhalation.
Another object of the invention is to provide a inhalation therapy device which does not significantly alter the mass median aerodynamic diameter of the aerosol delivered to the patient.
Another object of the invention is to provide a inhalation therapy device which delivers more aerosol to the patient than prior art.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein, the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.